Dilead(II) hydrogenphosphite dinitrate

In the title compound, Pb2(HPO3)(NO3)2, the two distinct Pb2+ ions (both with site symmetry m) adopt irregular PbO10 coordination polyhedra. The structure is completed by two distinct nitrate groups (in which one O atom and the N atom have m site symmetry for both ions) and an HPO3 2− anion (in which one O atom and the P and H atoms have m site symmetry). The connectivity of the PbO10, NO3 and HPO3 units in the crystal structure results in a three-dimensional network.

In the title compound, Pb 2 (HPO 3 )(NO 3 ) 2 , the two distinct Pb 2+ ions (both with site symmetry m) adopt irregular PbO 10 coordination polyhedra. The structure is completed by two distinct nitrate groups (in which one O atom and the N atom have m site symmetry for both ions) and an HPO 3 2À anion (in which one O atom and the P and H atoms have m site symmetry). The connectivity of the PbO 10 , NO 3 and HPO 3 units in the crystal structure results in a three-dimensional network.
The structure of (I) consists of two symmetry-independent nitrate groups and one HPO 3 hydrogenphosphite tetrahedron.
The Pb atoms are located between them in two different crystallographic positions, both of them being irregularly coordinated by ten O atoms ( Fig. 1). In the coordination of Pb1, shorter bonds occur causing larger bond valence sum (Brown & Altermatt, 1985) [2.028 (10) and 1.917 (6) for Pb(1)O 10 and Pb(2)O 10 , respectively]. On the other hand, the mean Pb-O distance is rather larger in Pb(1)O 10 than in Pb(2)O 10 , respectively 2.835 (5) Å and 2.745 (6) Å. These values are comparable to those reported in Pb(H 2 PO 4 ) 2 , 2.617 Å (Vasić et al., 1981). One can distinguish the two decahedrons by their respective coordination forms: one monodentate NO 3 and one monodentate HPO 3 occurs in the coordination of Pb1, while two bidentate NO 3 contribute to that of Pb2. Accordingly, the polyhedron Pb(1)O 10 turns to be more distorted as Pb (2) As expected, H1 atom bonded to P is not involved in any hydrogen bonding. Average P-O distance and O-P-O and H-P-O angles are 1.531 (5) Å, 110.4 (2)° and 108.6 (2)° respectively. d P-H = 1.20 (5) Å. These values lie in the same range as the ones previously reported in known phosphites (Ouarsal et al. 2005b).
Experimental 1.6161 g lead nitrate Pb(NO 3 ) 2 .6H 2 O was dissolved in 6 ml of distilled water and added to a solution of 0.4 g phosphorous acid H 3 PO 3 , dissolved in 5 ml water. The mixture was stirred for 1 h at 333 K, after which time the precipitate obtained was filtered out of the solution. The filtrate was allowed to stand at room temperature until many large, colourless needles of (I) arose. The crystals were recovered by filtration and washed with a water-ethanol (80:20 v/v) mixture.

Refinement
The H atom was located in a difference map and its position and U iso values were freely refined.

Special details
Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F 2 for refinement carried out on F and F 2 , respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement.
The program used for refinement, JANA2000, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger then the ones from the SHELX program.